On a U.S. government database somewhere, there is a classified court opinion that details unlawful surveillance of Americans’ communications. And the Justice Department is fighting to keep it secret.

Last year, Sen. Ron Wyden, D-Ore., revealed that the Foreign Intelligence Surveillance Court had found “on at least one occasion” that the government had conducted spying that was “unreasonable under the Fourth Amendment,” which is designed to prevent unreasonable searches and seizures. Wyden said that the FISC, which operates largely in secret, had found that the government acted unconstitutionally in how it had implemented so-called “minimization procedures” intended to limit how data on Americans are collected and retained. The senator added that the government was found to have “circumvented the spirit” of the Foreign Intelligence and Surveillance Act, a controversial spy law that civil liberties groups claim effectively allows “dragnet surveillance.”

When Wyden revealed the FISC ruling on the unlawful snooping, he did not disclose details about exactly what the surveillance involved or how many Americans were affected. But his comment prompted the Electronic Frontier Foundation to take legal action in an attempt to obtain more information. After filing suit in a district court, the rights group successfully established earlier this year that the Justice Department holds an 86-page FISC opinion, issued on Oct. 3, 2011, which appears to be the case Wyden cited. Now the EFF wants that opinion to be made public.

The DoJ said in a court memorandum filed in the district court case that it should not have to publish the secret opinion because doing so could cause “exceptionally grave and serious damage” to national security by revealing sources and methods. In addition, the DoJ claims that it could not elect to release the opinion even if it wanted to because publication would have to be approved by the FISC judge who authored it. In response, EFF has taken up the case directly with the FISC, which is now considering whether to release the documents on the unlawful surveillance. Last week, FISC Judge Reggie Walton ordered the DoJ to respond by June 7 to a motion filed by EFF requesting the release of the opinion, giving the department a fresh opportunity to advocate for non-disclosure.

The case comes at a particularly interesting time for the FISC, which has been the focus of calls from some lawmakers for less secrecy and more transparency on government surveillance. Late last year, during a debate on the renewal of FISA, Sen. Jeff Merkley, D-Ore., attempted to add an amendment to the spy law that would have made declassified versions of FISC opinions available to the public. Due to time constraints, the amendment was not passed, but Sen. Dianne Feinstein, D-Calif., chair of the Senate intelligence committee, vowed to work to add in Merkley’s amendment in the year ahead, saying that publishing declassified summaries of FISC opinions “can be done and I think it should be done.”

The EFF case offers the FISC an opportunity to pre-emptively embrace greater transparency. Of course, the DoJ is likely to argue strongly against the release of the controversial opinion on the unlawful snooping in line with a general trend toward excessive governmentsecrecy. But it should be possible to strike a balance between national security state secrets and the public’s right to know—especially when it comes to information about unconstitutional government surveillance.